The present invention relates to an antenna arrangement and more particularly to an antenna arrangement that includes an antenna reflector, an antenna holding unit, a transceiver element, a sensor unit and a signal detecting unit for processing signals arriving from a target and for generating on the basis of these signals control signals for guiding the antenna reflector into alignment with the target.
The antenna arrangement may be stationary or mounted on a moveable support surface, in other words intended for stationary equipment, land mobile equipment or marine equipment. The signal detecting unit includes a signal converter and a computing unit in series.
It is known to use in antenna arrangements of this kind separate pointing and tracking systems whose purpose is to optimise the bearing between, e.g., land-based antenna arrangements and satellites so as to obtain correct alignment therebetween. The investment costs in achieving optimal dynamic pointing accuracy with the antenna arrangement in such systems is very high. This antenna pointing accuracy can be influenced by externally acting forces, such as movement of the antenna supporting surface, the wind, and wave motion, for example.
Because the matter concerns an antenna arrangement and a target that move relative to one another, high demands are placed on the pointing system. These high demands, in turn, limit the choice equipment for detecting signals arriving from the target to solely extremely expensive equipment.
In view of the requirement of high dynamic pointing accuracy, mono-pulse technology is used. However, this technology normally requires high investment in signal detection equipment such as broadband spectrum analysers and the like in achieving the effect desired.
Several known systems lack the possibility of correcting for the drift and instability of primarily non-linear components used to provide information on reference data, and consequently these systems drift continuously in time with temperature and current.
The object of the present invention is to provide an antenna arrangement of the aforesaid kind which will solve the problem of continuously tracking a moveable signal source that is located above the horizon from a mobile antenna arrangement that is mounted on a moving object at a reasonable cost, i.e. at a cost which is substantially lower than what can be achieved at the present time.
In the case of an antenna arrangement of the aforedescribed kind that includes a signal converter and computing unit, It is proposed in accordance with the invention that the signal converter is adapted to reduce its bandwidth automatically and incrementally, wherewith a given bandwidth is activated and retained until a desired input signal can be detected within said bandwidth. The inventive antenna arrangement includes a system of sensors for sensing undesired changes in the alignment of the antenna reflector on he one hand and for setting and retaining a desired antenna position relative to a target object on the other hand; a group of sensors placed on the rear side of the reflector, and a further group of sensors placed on respective rotational axles. Both sensor groups are adapted to be set to zero when an optimal signal detection is achieved thereby that the frequency range of the signal converter is subjected to incremental reduction from one given bandwidth to the next lower bandwidth until the best possible signal value has been obtained.
The sensor system provides information relating to changes in the position of the antenna arrangement caused by external forces. This positional change is defined on the basis of speed data (xcex94Vx; xcex94Vy; xcex94Vz) which are integrated in a computing unit to obtain relative positional data. With knowledge of the data relating to the speed changes that have occured within an established time period, determined by the report time of the sensor system, the aforesaid information can be used as the input values for a superordinate computerised system control unit which sends these values to a drive unit for compensating for changes in the position of the antenna arrangement caused by said external forces.
In this regard, the sensor system can be used for at least two different purposes, such as to compensate for the external forces acting on the antenna arrangement as a result of movement of the surface on which the antenna arrangement is mounted, and also to detect a predetermined desired and allocated movement pattern of the antenna reflector and its tracking or a signal target that has a known orbit and/or a movement pattern calculated with the aid of the computing unit during an ongoing period of time.
The sensor system thus has overall responsibility for the ability of the antenna arrangement to compensate continuously for the influence of all external forces on said arrangement.
Correspondingly, it is important to obtain correct compensation data for the temperature dependency, ageing, etc., of the electronic components included in said arrangement, which may otherwise generate system drifts with respect to output data from all electronic components included in the system.